N1 Peak Research Articles

Investigating cold Aδ fibers in the 0–40 °C temperature range: A quantitative sensory testing and evoked potentials study

ObjectiveTo evaluate the activity of cold Aδ-type fibers to thermal stimuli above human skin temperature (i.e., >32 °C). MethodsTwenty young adults aged 20–24 years participated in this study. The cold-detection threshold was measured from a basal temperature of 40 °C using an adaptive staircase method with high-speed cooling ramps (170 °C/s). A total of 150 stimulations at 36 °C, 32 °C, 28 °C, 24 °C, 20 °C, 16 °C, 12 °C, 8 °C, 4 °C and 0 °C (15 each) were performed. After each stimulation, subjects estimated the intensity of cold sensation using a visual analog scale, and evoked potentials were recorded. ResultsThe average cold-detection threshold was 35 °C (SD = 1.8). Regardless of the stimulation temperature, subjects reported a cooling sensation. Interestingly, reported increments in sensation were prominent for stimulation temperatures between 32 °C and 20 °C, but below this latter temperature sensations varied only very slightly. Evoked potential recordings revealed that decreasing temperature stimuli from a baseline of 40 °C induced a previously unreported N2P2 component with a mean N2 peak latency of 275 ms (SD = 13.1). The peak-to-peak amplitude of the N2P2 complex increased as the intensity of the cooling stimulation increased, exhibiting a profile comparable to subject-perceived intensity, namely, a major increase up to 20 °C, followed by a plateau to 0 °C. ConclusionsThe cool sensations reported by subjects were likely conveyed by Aδ fibers rather than by slow-conducting C fibers. Moreover, our rapid stimulation technique starting from a high temperature (40 °C) was capable of a) generating cold sensations at stimulation temperatures between 36 °C and 32 °C, and b) revealing the optimal activation range of Aδ fibers (20 °C–28 °C). Any decrease in temperature below this range did not result in a significant increase in sensation and thus probably did not evoke a significant increase in Aδ fiber activity. SignificanceThe regular assessment of cold sensation in peripheral neuropathies (i.e., with temperatures below 32 °C), could be completed by investigating cold-detection thresholds at temperatures ranging from 40 °C to 32 °C. Indeed, the absolute threshold of cold perception appears to start at 35 °C. Changes in the activation threshold of cold fibers were more easily detectable at this level.

Nudging the N170 forward with prior stimulation-Bridging the gap between N170 and recognition potential.

Evoked response potentials are often divided up into numerous components, each with their own body of literature. But is there less variety than we might suppose? In this study, we nudge one component into looking like another. Both the N170 and recognition potential (RP) are N1 components in response to familiar objects. However, the RP is often measured with a forward mask that ends at stimulus onset whereas the N170 is often measured with no masking at all. This study investigates how inter‐stimulus interval (ISI) may delay and distort the N170 into an RP by manipulating the temporal gap (ISI) between forward mask and target. The results revealed reverse relationships between the ISI on the one hand, and the N170 latency, single‐trial N1 jitter (an approximation of N1 width) and reaction time on the other hand. Importantly, we find that scalp topographies have a unique signature at the N1 peak across all conditions, from the longest gap (N170) to the shortest (RP). These findings prove that the mask‐delayed N1 is still the same N170, even under conditions that are normally associated with a different component like the RP. In general, our results suggest greater synthesis in the study of event related potential components.

Early Functional and Cognitive Declines Measured by Auditory-Evoked Cortical Potentials in Mice With Alzheimer's Disease.

Alzheimer’s disease (AD) is characterized by a progressive loss of memory and cognitive decline. However, the assessment of AD-associated functional and cognitive changes is still a big challenge. Auditory-evoked cortical potential (AECP) is an event-related potential reflecting not only neural activation in the auditory cortex (AC) but also cognitive activity in the brain. In this study, we used the subdermal needle electrodes with the same electrode setting as the auditory brainstem response (ABR) recording and recorded AECP in normal aging CBA/CaJ mice and APP/PS1 AD mice. AECP in mice usually appeared as three positive peaks, i.e., P1, P2, and P3, and three corresponding negative peaks, i.e., N1, N2, and N3. In normal aging CBA mice, the early sensory peaks P1, N1, and P2 were reduced as age increased, whereas the later cognitive peaks N2, P3, and N3 were increased or had no changes with aging. Moreover, the latency of the P1 peak was increased as age increased, although the latencies of later peaks had a significant reduction with aging. In AD mice, peak P1 was significantly reduced in comparison with wild-type (WT) littermates at young ages, proceeding AD phenotype presentation. In particular, the later cognitive peak P3 was diminished after 3 months old, different from the normal aging effect. However, the latencies of AECP peaks in AD mice generally had no significant delay or changes with aging. Finally, consistent with AECP changes, the accumulation of amyloid precursor protein (APP) at the AC was visible in AD mice as early as 2 months old. These data suggest that AECP could serve as an early, non-invasive, and objective biomarker for detecting AD and AD-related dementia (ADRD).

Complete evaluation of retinal function in Major Depressive Disorder: From central slowdown to hyperactive periphery

BackgroundDeveloping easy-to-access biomarkers is crucial in Major Depressive Disorder. The retina has already been suggested as relevant. However, there is a need for a global and local assessment of whole retinal function using a reproducible, standardized protocol allowing for comparison across studies. Our aim is to assess whole retinal function in patients with actual unipolar Major Depressive Episode (MDE) using pattern, flash and multifocal electroretinogram (ERG) according to the International Society for Clinical Electrophysiology of Vision standardized protocols. MethodsWe assessed retinal function in 14 males and females with MDE, diagnosed based on the Diagnostic and Statistical Manual of Mental Disorders, and in age- and sex-matched healthy controls. ResultsComparing the patients with the controls, we observed the following using multifocal ERG: a significant increase in N1 peak time in ring 3 and a decrease in P1 amplitude in ring 2; using pattern ERG: a significant increase in P50 peak time; using flash ERG: a decrease in a- and b-wave peak time and an increase in the b-wave amplitude in dark-adapted 3.0, a decrease in a- and b-wave peak time and an increase in both wave amplitudes in light-adapted 3.0, and a decrease in the b-wave peak time in light-adapted flicker. LimitationsSample size. Contribution of pharmacological treatments to the outcomes cannot be formally excluded. ConclusionsPatients with MDE exhibit delayed signaling in the central retina and hyperreactivity to light in the periphery. Central retinal function may be a marker of psychomotor retardation and cognitive impairment in MDE.

Assessment of event-related evoked potentials and China-Wechsler intelligence scale for cognitive dysfunction in children with obstructive sleep apnea

ObjectiveTo explore the relationship between obstructive sleep apnea (OSA) and cognitive impairment by combining event-related evoked potentials (ERPs) and China-Wechsler Younger Children Scale (C-WISC) in children with sleep-disordered breathing (SDB) with vs. without OSA. MethodsThis was a retrospective case-control study of all consecutive children (n = 148) with adenoid tonsil hypertrophy between July 2017 and March 2019 at the Hospital. ResultsThe children were divided into the OSA (n = 102) and non-OSA (n = 46) groups. The apnea-hypopnea index (AHI), obstructive apnea index (OAI), and obstructive apnea-hypopnea index (OAHI) in the OSA group were elevated compared with those of the non-OSA group (all P < 0.001). The mean oxygen saturation (SaO2) and SaO2 nadir were lower in the OSA group compared with the non-OSA group (both P < 0.001). The respiratory arousal index (RAI) values in the OSA group were larger than those of the non-OSA group (P < 0.001). The P300 and N100 latencies in the OSA group were longer than those of the non-OSA group (both P < 0.001). Pearson's correlation analysis revealed correlations of the P300 peak latency with full-scale intelligence quotient (FIQ) (P < 0.001 and r = −0.527), verbal intelligence quotient (VIQ) (P < 0.001 and r = −0.448), and performance intelligence quotient (PIQ) (P < 0.001 and r = −0.515). There was a correlation between the N100 peak latency and PIQ (P = 0.026 and r = −0.183). ConclusionERPs, as an objective measurement, might help assess cognitive impairment in children with OSA.

Organic fertility inputs synergistically increase denitrification-derived nitrous oxide emissions in agroecosystems.

Soil fertility in organic agriculture relies on microbial cycling of nutrient inputs from legume cover crops and animal manure. However, large quantities of labile carbon (C) and nitrogen (N) in these amendments may promote the production and emission of nitrous oxide (N2 O) from soils. Better ecological understanding of the N2 O emission controls may lead to new management strategies to reduce these emissions. We measured soil N2 O emission for two growing seasons in four corn-soybean-winter grain rotations with tillage, cover crop, and manure management variations typical of organic agriculture in temperate and humid North America. To identify N2 O production pathways and mitigation opportunities, we supplemented N2 O flux measurements with determinations of N2 O isotopomer composition and microbiological genomic DNA abundances in microplots where we manipulated cover crop and manure additions. The N input from legume-rich cover crops and manure prior to corn planting made the corn phase the main source of N2 O emissions, averaging 9.8kg/ha of N2 O-N and representing 80% of the 3-yr rotations' total emissions. Nitrous oxide emissions increased sharply when legume cover crop and manure inputs exceeded 1.8 and 4Mg/ha (dry matter), respectively. Removing the legume aboveground biomass before corn planting to prevent co-location of fresh biomass and manure decreased N2 O emissions by 60% during the corn phase. The co-occurrence of peak N2 O emission and high carbon dioxide emission suggests that oxygen (O2 ) consumption likely caused hypoxia and bacterial denitrification. This interpretation is supported by the N2 O site preference values trending towards denitrification during peak emissions with limited N2 O reduction, as revealed by the N2 O δ15 N and δ18 O and the decrease in clade I nosZ gene abundance following incorporation of cover crops and manure. Thus, accelerated microbial O2 consumption seems to be a critical control of N2 O emissions in systems with large additions of decomposable C and N substrates. Because many agricultural systems rely on combined fertility inputs from legumes and manures, our research suggests that controlling the rate and timing of organic input additions, as well as preventing the co-location of legume cover crops and manure, could mitigate N2 O emissions.

Global motion evoked potentials in autistic and dyslexic children: A cross-syndrome approach

Atypicalities in psychophysical thresholds for global motion processing have been reported in many neurodevelopmental conditions, including autism and dyslexia. Cross-syndrome comparisons of neural dynamics may help determine whether altered motion processing is a general marker of atypical development or condition-specific. Here, we assessed group differences in N2 peak amplitude (previously proposed as a marker of motion-specific processing) in typically developing (n = 57), autistic (n = 29) and dyslexic children (n = 44) aged 6–14 years, in two global motion tasks. High-density EEG data were collected while children judged the direction of global motion stimuli as quickly and accurately as possible, following a period of random motion. Using a data-driven component decomposition technique, we identified a reliable component that was maximal over occipital electrodes and had an N2-like peak at ~160 msec. We found no group differences in N2 peak amplitude, in either task. However, for both autistic and dyslexic children, there was evidence of atypicalities in later stages of processing that require follow up in future research. Our results suggest that early sensory encoding of motion information is unimpaired in dyslexic and autistic children. Group differences in later processing stages could reflect sustained global motion responses, decision-making, metacognitive processes and/or response generation, which may also distinguish between autistic and dyslexic individuals.

Objective assessment of impulse control disorder in patients with Parkinson\u2019s disease using a low-cost LEGO-like EEG headset: a feasibility study

BackgroundPatients with Parkinson’s disease (PD) can develop impulse control disorders (ICDs) while undergoing a pharmacological treatment for motor control dysfunctions with a dopamine agonist (DA). Conventional clinical interviews or questionnaires can be biased and may not accurately diagnose at the early stage. A wearable electroencephalogram (EEG)-sensing headset paired with an examination procedure can be a potential user-friendly method to explore ICD-related signatures that can detect its early signs and progression by reflecting brain activity.MethodsA stereotypical Go/NoGo test that targets impulse inhibition was performed on 59 individuals, including healthy controls, patients with PD, and patients with PD diagnosed by ICDs. We conducted two Go/NoGo sessions before and after the DA-pharmacological treatment for the PD and ICD groups. A low-cost LEGO-like EEG headset was used to record concurrent EEG signals. Then, we used the event-related potential (ERP) analytical framework to explore ICD-related EEG abnormalities after DA treatment.ResultsAfter the DA treatment, only the ICD-diagnosed PD patients made more behavioral errors and tended to exhibit the deterioration for the NoGo N2 and P3 peak amplitudes at fronto-central electrodes in contrast to the HC and PD groups. Particularly, the extent of the diminished NoGo-N2 amplitude was prone to be modulated by the ICD scores at Fz with marginal statistical significance (r = − 0.34, p = 0.07).ConclusionsThe low-cost LEGO-like EEG headset successfully captured ERP waveforms and objectively assessed ICD in patients with PD undergoing DA treatment. This objective neuro-evidence could provide complementary information to conventional clinical scales used to diagnose ICD adverse effects.

Comparative Analysis of Cortical Auditory Evoked Potential in Cochlear Implant Users.

The primary goal of the study was to investigate electrical cortical auditory evoked potentials (eCAEPs) at maximum comfortable level (MCL) and 50% MCL on three cochlear implant (CI) electrodes and compare them with the acoustic CAEP (aCAEPs), in terms of the amplitude and latency of the P1-N1-P2 complex. This was achieved by comparing the eCAEP obtained with the method described and stimulating single electrodes, via the fitting software spanning the cochlear array and the aCAEP obtained using the HEARLab system at four speech tokens. Twenty MED-EL (MED-EL Medical Electronics, Innsbruck, Austria) CI adult users were tested. CAEP recording with HEARLab System was performed with speech tokens /m/, /g/, /t/, and /s/ in free field, presented at 55 dB SPL. eCAEPs were recorded with an Evoked Potential device triggered from the MAX Programming Interface (MED-EL Medical Devices) with 70 msec electrical burst at 0.9 Hz at the apical (1), middle (6), and basal (10 or 11) CI electrode at their MCL and 50% MCL. CAEP responses were recorded in 100% of the test subjects for the speech token /t/, 95% for the speech tokens /g/ and /s/, and 90% for the speech token /m/. For eCAEP recordings, in all subjects, it was possible to identify N1 and P2 peaks when stimulating the apical and middle electrodes. This incidence of detection decreased to an 85% chance of stimulation at 50% MCL on the same electrodes. A P1 peak was less evident for all electrodes. There was an overall increase in latency for stimulation at 50% MCL compared with MCL. There was a significant difference in the amplitude of adjacent peaks (P1-N1 and N1-P2) for 50% MCL compared with MCL. The mean of the maximum cross-correlation values were in the range of 0.63 to 0.68 for the four speech tokens. The distribution of the calculated time shift, where the maximum of the cross-correlation was found, was distributed between the speech tokens. The speech token /g/ had the highest number of valid cross-correlations, while the speech token /s/ had the lowest number. This study successfully compared aCAEP and eCAEP in CI users. Both acoustic and electrical P1-N1-P2 recordings obtained were clear and reliable, with good correlation. Latency increased with decreasing stimulation level, while amplitude decreased. eCAEP is potentially a better option to verify speech detection at the cortical level because it (1) uses direct stimulation and therefore creates less interference and delay of the sound processor and (2) creates more flexibility with the recording setup and stimulation setting. As such, eCAEP is an alternative method for CI optimization.

Motor adaptation and internal model formation in a robot-mediated forcefield.

Motor adaptation relies on error-based learning for accurate movements in changing environments. However, the neurophysiological mechanisms driving individual differences in performance are unclear. Transcranial magnetic stimulation (TMS)-evoked potential can provide a direct measure of cortical excitability. To investigate cortical excitability as a predictor of motor learning and motor adaptation in a robot-mediated forcefield. A group of 15 right-handed healthy participants (mean age 23 years) performed a robot-mediated forcefield perturbation task. There were two conditions: unperturbed non-adaptation and perturbed adaptation. TMS was applied in the resting state at baseline and following motor adaptation over the contralateral primary motor cortex (left M1). Electroencephalographic (EEG) activity was continuously recorded, and cortical excitability was measured by TMS-evoked potential (TEP). Motor learning was quantified by the motor learning index. Larger error-related negativity (ERN) in fronto-central regions was associated with improved motor performance as measured by a reduction in trajectory errors. Baseline TEP N100 peak amplitude predicted motor learning (P=0.005), which was significantly attenuated relative to baseline (P=0.0018) following motor adaptation. ERN reflected the formation of a predictive internal model adapted to the forcefield perturbation. Attenuation in TEP N100 amplitude reflected an increase in cortical excitability with motor adaptation reflecting neuroplastic changes in the sensorimotor cortex. TEP N100 is a potential biomarker for predicting the outcome in robot-mediated therapy and a mechanism to investigate psychomotor abnormalities in depression.

Characteristic Deviations of Auditory Evoked Potentials in Individuals with Autism Spectrum Disorder.

Neurological, structural, and behavioral abnormalities are widely reported in individuals with autism spectrum disorder (ASD); yet there are no objective markers to date. We postulated that by using dominant and nondominant ear data, underlying differences in auditory evoked potentials (AEPs) between ASD and control groups can be recognized. The primary purpose was to identify if significant differences exist in AEPs recorded from dominant and nondominant ear stimulation in (1) children with ASD and their matched controls, (2) adults with ASD and their matched controls, and (3) a combined child and adult ASD group and control group. The secondary purpose was to explore the association between the significant findings of this study with those obtained in our previous study that evaluated the effects of auditory training on AEPs in individuals with ASD. Factorial analysis of variance with interaction was performed. Forty subjects with normal hearing between the ages of 9 and 25 years were included. Eleven children and 9 adults with ASD were age- and gender-matched with neurotypical peers. Auditory brainstem responses (ABRs) and auditory late responses (ALRs) were recorded. Adult and child ASD subjects were compared with non-ASD adult and child control subjects, respectively. The combined child and adult ASD group was compared with the combined child and adult control group. No significant differences in ABR latency or amplitude were observed between ASD and control groups. ALR N1 amplitude in the dominant ear was significantly smaller for the ASD adult group compared with their control group. Combined child and adult data showed significantly smaller amplitude for ALR N1 and longer ALR P2 latency in the dominant ear for the ASD group compared with the control group. In our earlier study, the top predictor of behavioral improvement following auditory training was ALR N1 amplitude in the dominant ear. Correspondingly, the ALR N1 amplitude in the dominant ear yielded group differences in the current study. ALR peak N1 amplitude is proposed as the most feasible AEP marker in the evaluation of ASD.

A Low Power Multi-Class Migraine Detection Processor Based on Somatosensory Evoked Potentials

Migraine is a disabling neurological disorder that can be recurrent and persist for long durations. The continuous monitoring of the brain activities can enable the patient to respond on time before the occurrence of the approaching migraine episode to minimize the severity. Therefore, there is a need for a wearable device that can ensure the early diagnosis of a migraine attack. This brief presents a low latency, and power-efficient feature extraction and classification processor for the early detection of a migraine attack. Somatosensory Evoked Potentials (SEP) are utilized to monitor the migraine patterns in an ambulatory environment aiming to have a processor integrated on-sensor for power-efficient and timely intervention. In this work, a complete digital design of the wearable environment is proposed. It allows the extraction of multiple features including multiple power spectral bands using 256-point fast Fourier transform (FFT), root mean square of late HFO bursts and latency of N20 peak. These features are then classified using a multi-classification artificial neural network (ANN)-based classifier which is also realized on the chip. The proposed processor is placed and routed in a 180nm CMOS with an active area of 0.5mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The total power consumption is 249 μW while operating at a 20MHz clock with full computations completed in 1.31ms.

The early processing of fearful and happy facial expressions is independent of task demands – Support from mass univariate analyses

Most ERP studies on facial expressions of emotion have yielded inconsistent results regarding the time course of emotion effects and their possible modulation by task demands. Most studies have used classical statistical methods with a high likelihood of type I and type II errors, which can be limited with Mass Univariate statistics. FMUT and LIMO are currently the only two available toolboxes for Mass Univariate analysis of ERP data and use different fundamental statistics. Yet, no direct comparison of their output has been performed on the same dataset. Given the current push to transition to robust statistics to increase results replicability, here we compared the output of these toolboxes on data previously analyzed using classic approaches (Itier & Neath-Tavares, 2017). The early (0–352 ms) processing of fearful, happy, and neutral faces was investigated under three tasks in a within-subject design that also controlled gaze fixation location. Both toolboxes revealed main effects of emotion and task but neither yielded an interaction between the two, confirming the early processing of fear and happy expressions is largely independent of task demands. Both toolboxes found virtually no difference between neutral and happy expressions, while fearful (compared to neutral and happy) expressions modulated the N170 and EPN but elicited maximum effects after the N170 peak, around 190 ms. Similarities and differences in the spatial and temporal extent of these effects are discussed in comparison to the published classical analysis and the rest of the ERP literature.

Multifocal Electroretinography as a Method of Functional Assessment of Retinal Laser Injury in Experimental Studies

Purpose: to investigate local functional changes in the rabbit retina by multifocal electroretinography under pulsed laser radiation.Materials and methods. Transpupillary applications by single laser pulses (Nd:YAG laser, 532 nm, 50 ms) with the diameter of the laser beam spot on the retina surface of 132 µm (15 eyes) and 200 µm (15 eyes) were performed on 30 eyes of 15 rabbits. In each eye were applied 6 applications of different laser pulse power (15, 30, 50, 100, 150 and 200 mW). The diameter of the injury zone was assessed ophthalmoscopically and histologically. Multifocal electroretinography was performed before and 30 minutes after exposure using a module for multifocal electroretinography Neuro-ERG (Neurosoft, Russia), topographically comparing a pattern of 61 hexagons with an ophthalmoscopic fundus picture. The amplitude (µV) of the P1 peak and the implicit times (ms) of the P1 and N1 peaks were estimated in the first-order response in the hexagons corresponding to the laser damage zones.Results. When using a laser spot on the retina of 132 microns and 200 microns, the threshold level of laser radiation power for the development of significant local changes in the bioelectric activity of the retina was 50 and 30 mW, respectively (p &lt; 0.05). The minimal diameter of the laser damage at which significant functional changes are recorded by multifocal electroretinography with a pattern stimulator consisting of 61 hexagons was 127.2 ± 6.4 µm (spot 132 µm, energy 50 mW), while a significant relationship was found between changes in the peak amplitude P1 and ophthalmoscopic and histological dimensions of the damage zone (r = 0.73 and r = 0.71, respectively, p &lt; 0.01).Conclusion. The use of multifocal electroretinography can be used to quantify functional changes in local laser damage to the retina in experimental studies on rabbits.

Mitigating nitrogen pollution with under-sown legume-grass cover crop mixtures in winter cereals.

Nitrogen (N) pollution from N inputs to agricultural soils contributes to widespread eutrophication and global climate change. One period susceptible to N losses is between winter grain harvest in summer and corn planting in spring in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-winter grain rotation. Cover crops used to immobilize N during this period often depend on tillage, which can exacerbate N losses. Therefore, we evaluated whether reduced-till cover crops could decrease nitrate (NO3 - ) leaching and nitrous oxide (N2 O) emissions during this period. We tested this strategy in a cropping systems experiment on a 4-ha plot in central Pennsylvania over 2 yr. This experiment compared a clover (Trifolium pratense L.)-timothy (Phleum pratense L.) cover crop no-till underseeded into a standing spelt crop with a vetch (Vicia villosa Roth)-triticale (× Triticosecale Wittm. ex A. Camus) cover crop established with tillage after spelt harvest. These systems were compared based on fortnightly N2 O emissions using static chambers (n=4 per six sample dates) and potential NO3 - leaching using anion resin bags (n=4 per system per year). Reduced-till cover crops minimized peak N2 O emissions during the fall compared with tilled cover crops. However, reduced-till cover crops did not decrease potentially leachable NO3 - relative to tilled cover crops despite decreases in soil inorganic N. Cover crop N isotopes revealed that clover N may have mineralized and leached over the winter. Our results suggest that reduced-till cover crops can decrease N2 O emissions to mitigate the climate impact of agriculture but that winter-hardy cover crops should be chosen to mitigate leaching.

Constructing FeN4/graphitic nitrogen atomic interface for high-efficiency electrochemical CO2 reduction over a broad potential window

Summary Atomically dispersed Fe–N–C catalyst has shown great performance in the CO2-to-CO conversion, yet the high CO selectivity is achieved only within a rather narrow potential range, which cannot well meet the requirements for the following CO dimerization or hydrogenation. Here, we developed a hydrogen-pyrolysis etching strategy to precisely manipulate the uncoordinated N dopants in the Fe–N–C catalyst. This strategy could preferentially eliminate pyridinic and pyrrolic N atoms while leaving graphitic N. The resulting catalyst gave a CO faradaic efficiency (FECO) above 90% over a broad window from −0.3 to −0.8 V (versus RHE) (in particular, FECO > 97% at −0.6 V). In situ ATR-SEIRAS and first-principle calculations further revealed that this strategy can not only suppress the parasitic H2 generation but also promote CO2 activation and protonation with the assistance of co-adsorbed H2O on the “atomic interface” of “FeN4/graphitic N.”

Association of Chiropractic Colleges Research Agenda Conference 2021 Abstracts of Proceedings.

Association of Chiropractic Colleges Research Agenda Conference 2021 Abstracts of Proceedings.

It's all about time: precision and accuracy of Emotiv event-marking for ERP research.

BackgroundThe use of consumer-grade electroencephalography (EEG) systems for research purposes has become more prevalent. In event-related potential (ERP) research, it is critical that these systems have precise and accurate timing. The aim of the current study was to investigate the timing reliability of event-marking solutions used with Emotiv commercial EEG systems.MethodWe conducted three experiments. In Experiment 1 we established a jitter threshold (i.e. the point at which jitter made an event-marking method unreliable). To do this, we introduced statistical noise to the temporal position of event-marks of a pre-existing ERP dataset (recorded with a research-grade system, Neuroscan SynAmps2 at 1,000 Hz using parallel-port event-marking) and calculated the level at which the waveform peaks differed statistically from the original waveform. In Experiment 2 we established a method to identify ‘true’ events (i.e. when an event should appear in the EEG data). We did this by inserting 1,000 events into Neuroscan data using a custom-built event-marking system, the ‘Airmarker’, which marks events by triggering voltage spikes in two EEG channels. We used the lag between Airmarker events and events generated by Neuroscan as a reference for comparisons in Experiment 3. In Experiment 3 we measured the precision and accuracy of three types of Emotiv event-marking by generating 1,000 events, 1 s apart. We measured precision as the variability (standard deviation in ms) of Emotiv events and accuracy as the mean difference between Emotiv events and true events. The three triggering methods we tested were: (1) Parallel-port-generated TTL triggers; (2) Arduino-generated TTL triggers; and (3) Serial-port triggers. In Methods 1 and 2 we used an auxiliary device, Emotiv Extender, to incorporate triggers into the EEG data. We tested these event-marking methods across three configurations of Emotiv EEG systems: (1) Emotiv EPOC+ sampling at 128 Hz; (2) Emotiv EPOC+ sampling at 256 Hz; and (3) Emotiv EPOC Flex sampling at 128 Hz.ResultsIn Experiment 1 we found that the smaller P1 and N1 peaks were attenuated at lower levels of jitter relative to the larger P2 peak (21 ms, 16 ms, and 45 ms for P1, N1, and P2, respectively). In Experiment 2, we found an average lag of 30.96 ms for Airmarker events relative to Neuroscan events. In Experiment 3, we found some lag in all configurations. However, all configurations exhibited precision of less than a single sample, with serial-port-marking the most precise when paired with EPOC+ sampling at 256 Hz.ConclusionAll Emotiv event-marking methods and configurations that we tested were precise enough for ERP research as the precision of each method would provide ERP waveforms statistically equivalent to a research-standard system. Though all systems exhibited some level of inaccuracy, researchers could easily account for these during data processing.

Event-related potentials accompanying performance of computer mouse pointing task in the long-term dry immersion model of microgravity

Ten healthy volunteers participated in the ground imitation of a microgravity condition. For three weeks they stayed in the water filled tub without bodily support in supine position while isolated by waterproof material (this procedure is known as dry immersion - DI). During this period, they performed computer mouse pointing task and corresponding brain activity was evaluated by means of EEG: movement related and cognitive event-related potentials as well as resting state electroencephalogram were registered). Pointing task was performed before DI and at the time after initial period of adaptation – at the 5th and 17th days of DI. No deterioration of pointing task performance was found. Movement related potentials were not changed as well as cognitive peak P3, and only N1 peak significantly decreased at the 17th day of DI. Occipital alpha EEG also became significantly more pronounced at the 17th day of DI. Dry immersion procedure is thought to reproduce space flight physiological effects quite well, due to the DI specific feature – support withdrawal. Thus, results obtained indicate that support withdrawal also affects brain functioning in a specific way: increased alpha EEG is accompanied by altered visual processing (as indexed by diminished N1). Although these alterations are not sufficient to disrupt well learned mouse pointing task.

Diffusion transport over grain-boundary barriers as the origin of N1 deep level transient spectroscopy signal in [formula omitted] solar cells

In this work, we explore the hypothesis that the N1 peak in Cu(In,Ga)Se2 (CIGS) solar cells is caused by secondary barriers. We indicate, through numerical modelling of the corresponding Deep Level Transient Spectroscopy (DLTS) signal, that these barriers may be located at grain boundaries. Moreover, the proper reconstruction of the N1 signal using the double-barrier model requires an assumption that corresponding capacitance transients are due to the diffusion limited transport of holes over grain boundaries. Only then we were able to achieve sufficiently small values of the saturation current for realistic values of material parameters. We show that the position of the N1 DLTS peak and its activation energy depends on the effective density and the effective mobility of holes which can be calculated based on grain size and the properties of grain boundaries. This interpretation opens a room for the explanation of the unusual properties of the N1 signal in CIGS solar cells.